A generic-type gas turbine arrangement is shown in DE 1221497 and U.S. Pat. No. 4,348,157, in which to cool the rotor blades, which are attached on the rotor unit, cooling air is used, which is fed via cooling passages which extend inside stationary components of the gas turbine arrangement and, via correspondingly arranged cooling passage openings, impinges upon the rotor unit. On the rotor side, provision is also made for corresponding cooling air inlet openings into which at least some of the supplied cooling air flows. The transfer of the cooling air from the stationary components to the rotating rotor unit is carried out inside an annulus which on one side, axially to the rotor axis, is delimited by the rotor unit and by the stationary component. Adjoining radially on the inside is a further, inner annulus into which purging gas is introduced in order to protect components of the rotor unit close to the rotor shaft against friction-induced overheating. For operation-related reasons, the purging gas which directly envelops the rotor shaft is very intensely swirled and forms a heavily pronounced swirled flow inside the cavity. The pressure ratios in the respective regions of the gas turbine decrease as radial shaft spacing increases, i.e. the purging gas which is on the rotor shaft side is under a higher pressure compared with the pressure ratios inside the annulus, which in turn lie above the operating pressure ratios inside the hot gas passage.
A radially oriented leakage flow occurs and is directed from the inner side, i.e. from the cavity close to the rotor shaft, through the radially inner annular sealing arrangement into the cavity and from this through the radially outer annular sealing arrangement into the main gas passage. It becomes apparent in this case that the leakage flow which radially penetrates into the annulus is able to significantly disturb the cooling air flow which is provided there for the purpose of cooling the rotor unit and the flow direction of which is predominantly axially oriented, as a result of which the portion of cooling air flow which finds its way into the cooling medium inlet openings is reduced and the cooling effect and also the efficiency of the entire gas turbine arrangement which is associated therewith deteriorate considerably.
The cooling air only enters the turbine blade at the required pressure if it impinges with the designated flow direction. The more uniform the inflow is for entry into the blade root, the more favorable and more efficient is the arrangement.
In the previously cited printed publication, to this end it is proposed to provide a deflection device on the rotor side between the radially opposite annular sealing arrangements, which forces the leakage flow into radially extending passages so that a flow path for the leakage flow between the radially inner and outer annular sealing arrangements past the respective cooling passage openings is created.
Apart from the previously described feature of annular sealing arrangements not being fully gastight, as a result of which a leakage flow develops, it is necessary to ensure a controlled exchange of the purging gas which is introduced between the rotating and stationary installation components. For maintaining a determined exchange of purging gas, it is necessary to discharge this at least proportionately via corresponding connecting passages or leakage-conditioned annular sealing arrangements radially outwards, mostly into the operating passage of the respective rotating turbomachine. In the case of a turbine stage, therefore, the purging gas finds its way through corresponding intermediate gaps into the hot gas passage in which the purging gas intermixes with the hot gases.
In addition to the already explained flow disturbance which the leakage-conditioned purging gas flow exerts upon the cooling air flow which passes largely axially through the annulus, the high swirl portion of the purging gas flow, moreover, contributes towards the static pressure inside the annulus being reduced, as a result of which the cooling effect of the cooling air flow in the region of the rotor unit and of the rotor blades which are associated therewith is again weakened.